The effects of squatting while pregnant on pelvic dimensions: A computational simulation to understand childbirth

Assessment of the pelvic and body interface pressure during different recumbent and semi-recumbent birthing positions

BACKGROUND

Childbirth, a multifaceted physiological event, undergoes dynamic changes influenced significantly by the chosen birthing position, impacting comfort and maternal and neonatal outcomes among other factors. This study aimed to investigate the bed-body interface pressure across five commonly adopted birthing positions, particularly focusing on their influence on pelvic expansion biomechanics during labour.

METHODS

Twenty healthy participants, aged between 18 and 49 years, were evaluated. Interface pressure across multiple regions of interest, including the head, shoulder, pelvis, and full body, were meticulously assessed under different combinations of leg and back positioning.

FINDINGS

Significant variations in interface pressure were observed based on chosen positions. Post hoc pairwise comparisons showed different pressure distributions for all regions of interest, with the combination of legs in stirrups and a flat back resulting in the lowest average pressure in the pelvic region. During the closed glottis pushing task, this combination exhibited lower peak pressure and peak pressure index in the pelvic region compared to other positions.

INTERPRETATION

While upright positions are conventionally preferred, the study underscores the nuanced implications of recumbent and semi-recumbent positions. Although using stirrups with a flat back exerts less pressure, lying flat can impede blood flow and exacerbate pain, while stirrups might lead to discomfort and potential complications. Given these complexities, healthcare providers must consider multiple factors to determine optimal birthing positions. The interplay between birthing positions and obstetric outcomes awaits further exploration and refinement, marking an exciting frontier in maternal care.

Do all patients with history of pelvic ring injuries need a cesarean section? - A survey of orthopaedic and obstetric providers

OBJECTIVE(S)

The recommended mode of delivery following pelvic ring fractures with surgical fixation is unclear. The objective of this study was to assess expert opinions from orthopaedic surgeons and obstetrician gynecologists on their recommended delivery recommendations for pregnant individuals with a history of pelvic ring injury, and to see if there was any difference in recommendations between the two specialties, and what factors influenced recommendations.

STUDY DESIGN

An electronic, web-based survey was administered to a convenience sample of orthopaedic surgeons and obstetrician gynecologists, via advertisement to members of the Orthopaedic Trauma Association (OTA), the Society for Maternal Fetal Medicine, and querying obstetrician gynecologists practicing within the Military Health System. The survey was administered from November 2021 to December 2022. A two-proportion z-test, Chi-square or Fisher's Exact Test, and descriptive statistics were used to analyze data.

RESULTS

Survey respondents included 44 orthopaedic surgeons and 37 obstetricians. A total of 74 % obstetricians would recommend a trial of labor with hardware in place, while orthopaedic surgeon's recommendations varied based on the type of fixation. Forty four, 100 % of orthopaedic surgeons, recommended trial of labor if non-operative pelvic injury or unilateral posterior fixation only, 88 % recommended trial of labor if bilateral posterior fixation only, and 47.7 % for anterior trans-symphyseal plating only, 50 % for unilateral posterior and trans-symphyseal plating, and 43.2 % for bilateral posterior fixation with trans-symphyseal plating.

CONCLUSIONS

The results of these surveys demonstrate the lack of consensus as to the most appropriate birth plan for patients with a history of pelvic ring injuries. Vaginal delivery following pelvic ring fracture and fixation is possible, yet these patients are significantly more likely to undergo cesarean section than the general population. As such, we recommend that women who become pregnant after operative treatment of a pelvic ring injury develop an in-depth birthing plan with their obstetrician to determine the best course.

Impact of maternal posture on fetal physiology in human pregnancy: a narrative review

In numerous medical conditions, including pregnancy, gravity and posture interact to impact physiology and pathophysiology. Recent investigations, for example, pertaining to maternal sleeping posture during the third trimester and possible impact on fetal growth and stillbirth risk highlight the importance and potential clinical implications of the subject. In this review, we provide an extensive discussion of the impact of maternal posture on fetal physiology from conception to the postpartum period in human pregnancy. We conducted a systematic literature search of the MEDLINE database and identified 242 studies from 1991 through 2021, inclusive, that met our inclusion criteria. Herein, we provide a synthesis of the resulting literature. In the first section of the review, we group the results by the impact of maternal posture at rest on the cervix, uterus, placenta, umbilical cord, amniotic fluid, and fetus. In the second section of the review, we address the impact on fetal-related outcomes of maternal posture during various maternal activities (e.g., sleep, work, exercise), medical procedures (e.g., fertility, imaging, surgery), and labor and birth. We present the published literature, highlight gaps and discrepancies, and suggest future research opportunities and clinical practice changes. In sum, we anticipate that this review will shed light on the impact of maternal posture on fetal physiology in a manner that lends utility to researchers and clinicians who are working to improve maternal, fetal, and child health.

Evaluation of a short in-person and online antenatal educational intervention for high-risk pregnant women linked to antenatal consultation

INTRODUCTION

The aim of this study was to evaluate a short educational intervention that focused on labor pain (through visual analogue scale, VAS), postpartum anxiety, and birthing experience before and during the SARS-CoV-2 (COVID-19) pandemic.

METHODS

This was a quasi-experimental study conducted between November 2019 and May 2021 in Brazil in 100 women with a high-risk pregnancy in the third trimester of pregnancy with an intervention group with in-person or virtual sessions (during the COVID-19 pandemic) and a non-intervention group. The antenatal intervention included breathing and relaxation techniques, upright positions, and information about labor. For evaluation, an antenatal questionnaire, State-Trait Anxiety Inventory (STAI) and a postpartum questionnaire were used. For data analysis, Student's t-test, chi-squared and Fisher's exact tests, ANOVA, bivariate, and multivariate regression analysis, were used.

RESULTS

When comparing the women in the intervention group to the non-intervention group, it was observed that the latter group reported higher fear of pain at labor during antenatal consultations (p<0.013); more women needed analgesia at 0-4 cm dilation (17/40) (p<0.018); the duration of labor was ≥12 hours (37/50) (p<0.037); while the intervention reported having a regular, good or excellent labor period (36/50) (p=0.014). The multiple regression analysis for labor pain showed a significant relationship between mode of delivery (cesarean delivery: RR; SE -21.43; 5.32, p<0.001) and labor pain, and good satisfaction with labor (RR; SE -13.86; 6.40, p=0.033).

CONCLUSIONS

Women from the intervention group had more satisfaction and less pain during labor than women from the non-intervention group.

The impact of femoral rotation on sacroiliac articulation during pregnancy. Is there evidence to support Farabeuf's hypothesis by finite element modelization?

BACKGROUND

Counter-nutation movement is deemed crucial during the management of the birth process. It is a combination of lateral ilia expansion and backward displacement of the promontory resulting from the external rotations of the femurs producing an enlargement of the pelvic inlet. However, since its description by Farabeuf, this mechanism has never been challenged and analyzed in a dynamic finite element study.

METHODS

Based on a female pelvic mesh and sacroiliac ligaments, we simulated external rotations of both femurs with imposed rotation of the two acetabulum centers. We hypothesize that lateral ilia expansion generates a sacrum movement resulting in a backward displacement of the promontory and a pelvic inlet enlargement.

RESULTS

Finite element simulation confirms our hypothesis and reveals that ilio-sacro-transverse and axile ligaments play an essential role in this mechanism. Indeed, the increase in stiffness (ranging from 500 MPa to 750 MPa) of these ligaments accentuates the counter-nutation movement and the opening of the inlet. Instead of the anatomic congruence between the ilium and the sacrum, the sacroiliac ligaments may explain the counter-nutation. After a 6° of femur rotation, the inlet area increases to 11 cm2 (141 cm2 vs. 130 cm2). This enlargement could be noteworthy in case of obstructed labor or shoulder dystocia. Moreover, the association between external rotation and flexion of the femurs could be more efficient for opening the pelvic inlet.

CONCLUSIONS

Our result did not support the original assumption of Farabeuf. By revealing how postural adjustment increases the bony birth canal, this study provides essential information for the clinical management of the delivery.

Predicting mid-pelvic interspinous distance in women using height and pubic arch angle

OBJECTIVE

To predict the interspinous distance (ISD) using the relationship between female height and pelvimetric measures on magnetic resonance (MR) images.

METHODS

We obtained measurements of the pubic arch angle (PAA), inlet-anteroposterior (AP) distance, mid-pelvis AP distance, outlet-AP distance, ISD, and ischial tuberosity distance using 710 pelvic MR images from nonpregnant reproductive-aged (21-50 years) women from January 2014 to June 2020. Patient height was also assessed from medical records. We determined the formula for predicting ISD using multiple regression analysis.

RESULTS

The mean ± standard deviation of the height, PAA, inlet-AP distance, mid-pelvis AP distance, outlet-AP distance, ISD, and ischial tuberosity distance were 160.0 ± 5.5 cm, 87.31 ± 6.6°, 129.7 ± 9.0 mm, 119.7 ± 8.5 mm, 111.71 ± 8.90 mm, 108.88 ± 8.0 mm, and 121.97 ± 11.8 mm, respectively. Two significant regression formulas for predicting ISD were identified as follows: ISD = 0.24973 × height - 0.06724 × inlet-AP distance + 0.12166 × outlet-AP distance + 0.29233 × ischial tuberosity distance + 0.32524 × PAA (P < 0.001, R2 = 0.9973 [adjusted R2 = 0.9973]) and ISD = 0.40935 × height + 0.49761 × PAA (P < 0.001, R2 = 0.9965 [adjusted R2 = 0.9965]).

CONCLUSION

ISD is the best predictor of obstructed labor. This study predicted ISD with 99% explanatory power using only the height and PAA. The PAA can be measured by transperineal ultrasound. This formula may successfully predict vaginal delivery or cephalopelvic disproportion.

Birthing balls to decrease labor pain and peanut balls to decrease length of labor: what is the evidence?

Birthing balls and peanut balls have been used for decades by nurses and midwives as a nonpharmacologic adjunct to labor management based on anecdotal evidence. This article aimed to review the evidence regarding their safety and efficacy based on randomized controlled trials. Birthing balls are round exercise balls that a laboring individual can use for sitting, rocking, and pelvic rotation. The use of the birthing balls has been thought to increase maternal comfort and mimic upright positioning to widen the pelvic outlet for those laboring without an epidural. A recent meta-analysis showed that the use of the birthing ball in labor significantly reduces maternal pain in labor by 1.7 points on a standard visual analog scale of 1 to 10 (mean difference, -1.70 points; 95% confidence interval, -2.20 to -1.20). The use of the birthing ball does not significantly affect the mode of delivery or the rate of other obstetrical complications. This suggests that its use is safe and can offer subjective improvement in maternal pain experienced during labor. The peanut ball is a peanut-shaped plastic ball placed between the knees of a person laboring in the lateral recumbent position, a position common in those laboring with an epidural. Traditionally, its use has been thought to allow for bent-knee positioning that can mimic a squatting position and facilitate frequent and optimal position changes during labor. Data regarding the effects of the peanut ball are mixed. A recent systematic review and meta-analysis found that the use of the peanut ball compared with no peanut ball is associated with a significantly decreased first stage of labor (mean difference, -87.42 minutes; 95% confidence interval, -94.49 to -80.34) and an 11% higher relative risk of vaginal delivery (relative risk, 1.11; 95% confidence interval, 1.02-1.22; n=669). The use of the peanut ball is not associated with increased incidences of obstetrical complications. As such, it is reasonable to offer to individuals in labor. There has been no reported risk of the use of either the birthing ball or the peanut ball. As such, both interventions can be offered to individuals in labor as an adjunct to labor management techniques based on moderate quality evidence.

Alternative Birthing Positions Compared to the Conventional Position in the Second Stage of Labor: A Review

The position in which the woman delivers has a lot of impact on the ease of delivery. Women's satisfaction with their birthing experience and the care they receive is significantly impacted by the fact that giving birth is frequently a challenging experience. Birthing positions refer to various postures which can be assumed at the time of delivery by a pregnant woman. Currently, the majority of women give birth either while lying flat on their backs or in a semi-sitting position. Upright positions, which include standing, sitting, or squatting along with side-lying and hands-and-knees, are less common birth positions. Doctors, nurses, and midwives are among the most important healthcare professionals, having a significant influence in deciding which position the woman will give birth in and on the physiological and psychological effects of the experience of a woman in labor. There isn't much research to back up the best position for mothers during the second stage of labor. This review article aims to review and compare the advantages and risks of common birthing positions and know about the knowledge of alternative birthing positions among pregnant women.

Influence of Laboring People's Mobility and Positional Changes on Birth Outcomes in Low-Dose Epidural Analgesia Labor: A Systematic Review with Meta-Analysis

INTRODUCTION

Freedom of movement has been identified as a key issue for pregnant individuals during the birthing process, even if they opt for epidural analgesia, which has relegated people to more static positions during birth for many years. The aims of this systematic review were to evaluate the influence of mobility and positional changes on perinatal and neonatal outcomes in people in labor with epidural analgesia, describe the range of movement interventions used during the first and second stage of labor, and describe the level of motor blockade among people with low-dose epidural analgesia.

METHODS

Bibliographic databases (Web of Science, Cochrane, CINAHL) were consulted from December 2020 to January 2021. The articles selected were clinical trials and observational or analytical studies, the subject of which was mobilization during labor in people with epidural analgesia. The outcome measures were mode of birth, duration of labor, and extrauterine adaptation after birth. A narrative synthesis was used to describe the types of movements interventions employed during the stages of labor and the level of motor blockade among people with low-dose epidural analgesia.

RESULTS

Ten articles were selected (8 clinical trials, one cross-sectional study, and one quasiexperimental study), with a total sample of 6086 individuals. A meta-analysis showed nonsignificant results between groups for mode of birth (relative risk [RR], 1.00; 95% CI, 0.87-1.14), duration of labor (RR, 1.64; 95% CI, -34.57 to 37.86), and extrauterine adaptation after birth (RR, 0.86; 95% CI, 0.39-1.93). There was heterogeneity among studies in the type of movement interventions used during the first and second stage of labor.

DISCUSSION

Although no clear benefit was observed for mobilization in epidural labor, no detrimental effects were found either, so perinatal care providers should encourage mobilization if the laboring person so desires, throughout the entire childbirth process.

[Good practices, interventions, and results: a comparative study between a birthing center and hospitals of the Brazilian Unified National Health System in the Southeastern Region, Brazil]

This study aims to compare obstetric care in a birthing center and in hospitals of the Brazilian Unified National Health System (SUS) considering good practices, interventions, and maternal and perinatal results in the Southeast Region of Brazil. A cross-sectional study was conducted with comparable retrospective data from two studies on labor and birth. A total of 1,515 puerperal women of usual risk of birthing centers and public hospitals in the Southeast region were included. Propensity score weighting was used to balance the groups according to the following covariates: age, skin-color, parity, membrane integrity, and cervix dilation at hospitalization. Logistic regressions were used to estimate odds ratios (OR) and 95% confidence intervals (95%CI) between the place of birth and outcomes. In birthing centers, compared to hospitals, the puerperal woman had a higher chance of having a companion (OR = 86.31; 95%CI: 29.65-251.29), eating or drinking (OR = 862.38; 95%CI: 120.20-6,187.33), walking around (OR = 7.56; 95%CI: 4.65-12.31), using non-pharmacological methods for pain relief (OR = 27.82; 95%CI: 17.05-45.40), being in an upright position (OR = 252.78; 95%CI: 150.60-423.33), and a lower chance of using oxytocin (OR = 0.22; 95%CI: 0.16-0.31), amniotomy (OR = 0.01; 95%CI: 0.01-0.04), episiotomy (OR = 0.01; 95%CI: 0.00-0.02), and Kristeller maneuvers (OR = 0.01; 95%CI: 0.00-0.02). Also, in birthing centers the newborn had a higher chance of exclusive breastfeeding (OR = 1.84; 95%CI: 1.16-2.90) and a lower chance of airway (OR = 0.24; 95%CI: 0.18-0.33) and gastric aspiration (OR = 0.15; 95%: 0.10-0.22). Thus, birthing centers offers a greater supply of good practices and fewer interventions in childbirth and birth care, with more safety and care without influence on the outcomes.

Effect of different squatting exercises on menstrual aspects, pelvic mechanics and uterine circulation in primary dysmenorrhoea: a randomised controlled trial

This was a randomised trial aimed to determine squatting exercises' effects on menstruation, pelvic mechanics, and uterine circulation in primary dysmenorrhoea. A total of 120 females with primary dysmenorrhoea were assigned into group (A), receiving yoga protocol, or groups (B, C & D), receiving yoga protocol added to modified wall squat, sumo squat, or deep squat, respectively. Menstrual pain and distress, pelvic inclination, and uterine circulation were measured before and after interventions using a pain scale, a questionnaire, palpation metre, and Doppler ultrasonography, respectively. There was a significant reduction in pain intensity in groups B & C (effect size = 3.97 & 5.89, respectively), compared to group A (effect size = 3.68), and in group C (effect size = 5.89) compared to group D (effect size = 3.94), pain subscale in the groups B, C & D (effect size = 1.69, 3.3 & 3.41, respectively), compared to group A (effect size= 2.47), water retention subscale in group D effect size 0.90 compared to group A (effect size =0.41) and in the questionnaire total scores in the groups C &D (effect size = 2.3 & 2.46, respectively) when compared to group A (effect size =1.94). Adding squatting exercises to yoga is more effective than yoga alone in reducing menstrual pain and distress.IMPACT STATEMENTWhat is already known on this subject? Physical exercises positively affect primary dysmenorrhoea in terms of decreased pain and distress, possibly through altering faulty posture. Squatting exercises affect lumbopelvic mechanics.What do the results of this study add? This study explores the effect of squatting exercises on pelvic inclination, menstrual aspects, and circulation.What are the implications of these findings for clinical practice and/or further research? Squatting exercises can be utilised to affect pelvic mechanics leading to decreased menstrual pain and distress, because of decreased pelvic congestion.

Textbook typologies: Challenging the myth of the perfect obstetric pelvis

Medical education's treatment of obstetric-related anatomy exemplifies historical sex bias in medical curricula. Foundational obstetric and midwifery textbooks teach that clinical pelvimetry and the Caldwell-Moloy classification system are used to assess the pelvic capacity of a pregnant patient. We describe the history of these techniques-ostensibly developed to manage arrested labors-and offer the following criticisms. The sample on which these techniques were developed betrays the bias of the authors and does not represent the sample needed to address their interest in obstetric outcomes. Caldwell and Moloy wrote as though the size and shape of the bony pelvis are the primary causes of "difficult birth"; today we know differently, yet books still present their work as relevant. The human obstetric pelvis varies in complex ways that are healthy and normal such that neither individual clinical pelvimetric dimensions nor the artificial typologies developed from these measurements can be clearly correlated with obstetric outcomes. We critique the continued inclusion of clinical pelvimetry and the Caldwell-Moloy classification system in biomedical curricula for the racism that was inherent in the development of these techniques and that has clinical consequences today. We call for textbooks, curricula, and clinical practices to abandon these outdated, racist techniques. In their place, we call for a truly evidence-based practice of obstetrics and midwifery, one based on an understanding of the complexity and variability of the physiology of pregnancy and birth. Instead of using false typologies that lack evidence, this change would empower both pregnant people and practitioners.

Evaluating the effects of maternal positions in childbirth: An overview of Cochrane Systematic Reviews

INTRODUCTION

The purpose of this study is to conduct an overview of Cochrane systematic reviews (SRs) evaluating the effects of maternal positions in childbirth in order to compile existing evidence for relevant research questions that have been addressed by more than one review, to provide a succinct summary of the up-to-date evidence and to identify areas for future research.

METHODS

An electronic search was conducted in the Cochrane database. Two primary outcomes were the duration of labor and birth, and operative birth. The quality of included reviews was assessed using the AMSTAR criteria, and the quality of the evidence was rated using the GRADE criteria.

RESULTS

We included 3 Cochrane SRs. There was a significant mean difference (MD) found in the duration of the first stage by 1 hour and 22 minutes (MD= -1.21; 95% CI: -2.35 - -0.07, I2=94%) and reduction in caesarean section rates (RR=0.71; 95% CI: 0.54-0.94, I2=0%) in the upright birth position group compared with the horizontal. Also, there was a statistically significant difference in the duration (minutes) of the second stage of labor (MD= -6.16; 95% CI: -9.74 - -2.59, I2=91%) and a reduction in assisted vaginal birth rates (RR=0.75, 95% CI: 0.66-0.86, I2=29%) in the upright group compared with the horizontal without epidural analgesia. The quality of evidence within the reviews was very low to moderate.

CONCLUSIONS

There is currently a limited body of evidence to clearly assess the benefits and risks of assuming upright positions during childbirth. The overview highlights the need for high-quality research studies, involving better definition and comprehensive assessment of the effects of squatting during childbirth.

Can the Dynamic External Pelvimetry Test in Late Pregnancy Reveal Obstructed and Prolonged Labor? Results From a Pilot Study

Background The size and mobility of the maternal pelvic space are fundamental factors in successful childbirth and can allow operators to screen for dystocia. This pilot study including a group of 70 pregnant women aimed to test whether the external dynamic pelvimetry test can be used to predict the likelihood of obstructed labor. Methodology The study cohort consisted of 70 pregnant women in their third trimester. The cohort was divided retrospectively into an obstructed labor group and a control group. Obstructed labor was defined using the following obstetric outcomes: augmentation with oxytocin from the first phase of the dilating period, Kristeller's maneuvers, vacuum extractor (kiwi), forceps, and the cesarean section following the onset of labor. Results The measurements obtained for the longitudinal hemi-diameter of Michaelis, the inter-tuberous diameter, and the base of the Trillat's triangle were statistically significant in every position. The difference in the measurements of the transverse diameter of Michaelis between standing and hands-and-knees position and the difference in the sizes of the bi-cristal diameter between hands-and-knees and squatting position were statistically significant. Conclusions Dimension and biomechanical properties of the pelvic tissue and spaces influence the evolutionary childbirth process. After clinical confirmation on a large population, hypomobility of specified external pelvic diameters measured in shifting positions can become a screening tool to detect the contracted pelvis and prevent damage caused by dystocia and prolonged labor in women and newborns.

The obstetrical dilemma hypothesis: there's life in the old dog yet

The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.

Pelvic capacity in pregnant women, identified using magnetic resonance imaging

INTRODUCTION

Maternal pelvic capacity plays a major role during childbirth because the passage of the fetus through the bony birth canal enables vaginal birth. Maternal birthing position may influence pelvic capacity because upright positions optimize capacity, possibly due to free movement of the pelvic joints. Herein, pelvic capacity was assessed by comparing changes in pelvic dimensions across pregnancy and in three birthing positions.

MATERIAL AND METHODS

This diagnostic imaging study of 50 pregnant women was conducted at Aarhus University Hospital, Denmark. Pelvic measurements were obtained with 1.5 T magnetic resonance pelvimetry during gestational weeks 20 and 32, in three birthing positions: kneeling squat, semi-lithotomy and supine. Pelvic capacity was compared between gestational weeks and positions.

RESULTS

In all three positions there is an overall increase in pelvic capacity from gestational week 20-32 at both the pelvic inlet and outlet. Comparing pelvic capacity at gestational week 32 between the semi-lithotomy and supine positions revealed that the pelvic inlet was larger in the supine position, whereas the mean pelvic outlet was 0.2 cm (p < 0.001) larger in the semi-lithotomy position. Likewise, the pelvic inlet was larger in the supine than in the kneeling squat position. Shifting from supine to kneeling squat position increased the midplane and pelvic outlet dimensions by up to 1 cm (p < 0.001).

CONCLUSIONS

The finding herein of an increased pelvic capacity as the pregnancy progresses is novel. Further, the results indicate that the supine position is optimal for increasing pelvic inlet size, whereas the semi-lithotomy and kneeling squat positions are optimal for increasing mid- and outlet-pelvic capacities.

Effect of the birthing position on its evolution from a biomechanical point of view

BACKGROUND AND OBJECTIVE

During vaginal delivery, several positions can be adopted by the mother to be more comfortable and to help the labor process. The positions chosen are very influenced by factors such as monitoring and intervention during the second stage of labor. However, there is limited evidence to support the most ideal birthing position. This work aims at contributing to a better knowledge associated with the widening of the pubic symphysis and the biomechanics of flexible and non-flexible sacrum positions that can be adopted during the second stage of labor, as well as their resulting pathophysiological consequences.

METHODS

A validated computational model composed by the pelvic floor muscles attached to the bones, and a fetus head was used to simulate vaginal deliveries. This model was modified to mimic two birthing positions: one that allows the free movement of the coccyx as in flexible sacrum positions and other in which this movement is more restricted as in non-flexible sacrum positions. The widening of the pubic symphysis was also considered to facilitate the passage of the fetus head.

RESULTS

The results obtained showed that, in non-flexible sacrum positions, where the coccyx movement is restricted, occur a rotation of 3.6° of the coccyx and a widening of 6 mm of the pubic symphysis. In contrast, in flexible sacrum positions, where the coccyx is free to move, occur a rotation of 15.7° of the coccyx and a widening of the pubic symphysis of 3 mm, appearing to be more beneficial for the mother's pelvis, but slightly higher stresses were detected in the pelvic floor muscles.

CONCLUSIONS

Globally, the results obtained allow to conclude that different birthing positions lead to changes in the female pelvic space, so certain positions can be adopted by the mother during the second stage of labor to reduce the risk of obstructed labor and the development of several dysfunctions. More specifically, flexible sacrum positions, such as kneeling, standing, squatting and sitting positions, are more beneficial for the bone structure of her pelvis as they allow a higher coccyx movement and lower widening of the pubic symphysis.

Dynamic External Pelvimetry Test in Third Trimester Pregnant Women: Shifting Positions Affect Pelvic Biomechanics and Create More Room in Obstetric Diameters

Dystocia in labor is still a clinical challenge. The "contracted pelvis" is the absence of pelvic mobility, which leads to fetal-pelvic disproportion, obstructed labor, and operative delivery. Maternal pelvis biomechanics studies by high technological techniques have shown that maternal shifting positions during pregnancy and labor can create more room in the pelvis for safe delivery. The external and internal pelvic diameters are related. The present study aims to evaluate the external obstetric pelvic diameters in shifting positions using a clinical technique suitable for daily practice in every clinical setting: the dynamic external pelvimetry test (DEP test). Seventy pregnant women were recruited, and the obstetric external pelvic diameters were measured, moving the position from kneeling standing to "hands-and-knees" to kneeling squat position. Results showed modification of the pelvic diameters in shifting position: the transverse and longitudinal diameters of Michaelis sacral area, the inter-tuberosities diameter, the bi-trochanters diameter, and the external conjugate widened; the bi-crestal iliac diameter, the bi-spinous iliac diameter, and the base of the Trillat's triangle decreased. The test showed good reproducibility and reliability. Linear correlations were found between diameters and between the range of motion of the diameters. The maternal pelvis is confirmed to modify the diameters changing its tridimensional shape. The pelvic inlet edge's inclination is inferred to be modified, facilitating the fetal descend. The pelvic outlet enlarged the transverse diameter, facilitating birth. The DEP test estimates the pelvic diameters' modification with postural changes, as magnetic resonance (MR) and computational biomechanics studies have demonstrated.

Measurement of pubic symphysis width in different birthing positions using ultrasound

Studies have shown that some vertical birthing positions, such as squatting and standing, may influence labour and childbirth. However, a rigorous biomechanical understanding of how different positions affect a woman's pelvis during labour is currently lacking. It was hypothesized that the position of pubic bones is affected in different positions, and thus the pubic symphysis width changes. Therefore, we measured pubic symphysis width on eleven women in their seventh to ninth months of pregnancy in different positions through three-dimensional (3D) reconstruction of pubic symphysis ultrasound images. Positions studies included those used in clinics like supine and lithotomy positions, in addition to squatting and standing, which are recommended by midwives. The results showed that the average superior and inferior pubic symphysis widths in lithotomy, squatting and standing positions were approximately 1 mm larger than those in the supine position. However, no significant difference between lithotomy, squatting and standing positions was found. The results were consistent with those of two comparable studies. A significant difference was only found between standing and squatting, standing and lithotomy in the rotation angle about the medio-lateral axis. The results suggest that positions with thigh hyperflexion and gravity effect make a difference in pubic symphysis width and might have a positive effect in childbirth. However, due to the small sample size, no definite conclusion can be drawn.

Squatting position in the second stage of labor: A systematic review and meta-analysis

OBJECTIVES

The influence of squatting during delivery on maternal and fetal outcomes remains unclear. We performed a systematic review and meta-analysis to evaluate the benefits and risks of adopting a squatting position during the second stage of labor.

STUDY DESIGN

Search Strategy: A systematic search in the three major electronic databases (CENTRAL, PubMed and Embase) was performed, from their respective inception dates to the 14th of December 2019, using 'squatting', and a combination of keywords to identify delivery. Eligibility criteria: Randomized controlled trials comparing squatting position to any supine position during the second stage of labor.

STATISTICAL ANALYSES

Risk ratio for dichotomous outcomes, mean difference for continuous outcomes, with 95 % confidence intervals. Fixed-effects meta-analysis (Mantel-Haenszel method) or random-effects model (inverse variance method), for low and high heterogeneity between trials, respectively. PROSPERO Registration number: CRD42018093244 RESULTS: Seven randomized controlled trials (n = 1219) were included. Three studies were assessed as low risk of bias, three others as moderate and one study as high risk of bias. The main limitation is the lack of reporting on the methods to achieve randomization and concealment of allocation in most of the studies. There was no difference in the duration of the second stage of labor (mean -11.09 min; 95 %CI -38.85 to 16.68). In the squatting group, the risk of caesarean section was increased (RR 2.26, 95 %CI 1.07-4.80) and the risk of instrumental delivery was decreased (RR 0.60, 95 %CI 0.45-0.81), which results in a similar probability of spontaneous delivery. There were no differences regarding the other maternal and fetal outcomes.

CONCLUSIONS

The available evidence does not show the squatting position during childbirth to be beneficial. As there is no evidence for or against squatting, women should be able to choose the position they prefer.

Estimating the Mobility of the Michaelis Sacral Rhombus in Pregnant Women

Pelvic mobility is the cornerstone of an adequate birth canal for safe childbirth, and midwives invite pregnant women to assume loading positions to facilitate delivery. Biomechanics asserts that pelvic space changes in shifting positions from erect to the squat position. The current standard practice in obstetrics and osteopathy provides a qualitative observational assessment of the dimension of Michaelis sacral rhombus in shifting positions; a previous report presented a clinical method and instrument to estimate the pelvic range of motion through finger contact on bone landmarks. The present study aims to match the measurement of the diameters of the sacral area of Michaelis from skin marks with the amount from bone landmarks. Methods estimate the sacral area from 100 pregnant women in the late trimester, considering the dimension of the diameters, the range of motion, and the patterns of mobility. Differences resulted in the methods: measuring the skin marks in shifting positions revealed a not significant difference between starting position and squat position. The measurements through the finger contact on the bone landmarks seem to be adequate to estimate pelvic mobility fulfilling the expectation from biomechanics literature.

Association of objectively measured physical fitness during pregnancy with maternal and neonatal outcomes. The GESTAFIT Project

Aim

To analyse i) the association of physical fitness during early second trimester and late pregnancy with maternal and neonatal outcomes; and ii) to investigate whether physical fitness is associated with the type of birth (vaginal or caesarean section).

Methods

Pregnant women from the GESTAFIT Project (n = 159) participated in this longitudinal study. Maternal physical fitness including upper- and lower-body strength, cardiorespiratory fitness (CRF) and flexibility were measured through objective physical fitness tests at the 16^th and 34^th gestational weeks. Maternal and neonatal outcomes were collected from obstetric medical records. Umbilical arterial and venous blood gas pH and partial pressure of carbon dioxide (PCO₂) and oxygen (PO₂), were assessed.

Results

At the 16^th week, greater upper-body muscle strength was associated with greater neonatal birth weight (r = 0.191, p<0.05). Maternal flexibility was associated with a more alkaline arterial pH (r = 0.220, p<0.05), higher arterial PO₂ (r = 0.237, p<0.05) and lower arterial PCO₂ (r = -0.331, p<0.01) in umbilical cord blood. Maternal CRF at the 16^th gestational week was related to higher arterial umbilical cord PO₂ (r = 0.267, p<0.05). The women who had caesarean sections had lower CRF (p<0.001) at the 16^th gestational week and worse clustered overall physical fitness, both at the 16^th (-0.227, p = 0.003, confidence interval (CI): -0.376, -0.078) and 34^th gestational week (-0.223; p = 0.018; CI: -0.432, -0.015) compared with the women who had vaginal births.

Conclusion

Increasing physical fitness during pregnancy may promote better neonatal outcomes and is associated with a decrease in the risk of caesarean section.

This trial was registered at ClinicalTrials.gov (NCT02582567) on October 20, 2015.

A Postural Approach to the Pelvic Diameters of Obstetrics: The Dynamic External Pelvimetry Test

In recent years, there has been a renewed interest in internal and external pelvimetry, in relation to the diagnosis of dystocia from a "contracted pelvis." Dystocia is still one of the causes of maternal-fetal morbidity and mortality in the world. The main cause is the fetal-pelvic disproportion, of which mechanical dystocia and contracted pelvis are most probably involved. Clinical pelvimetry was the diagnostic method of "contracted pelvis" and still seems to have its place in the clinical obstetric routine. Studies have been conducted in order to measure anatomical diameters and correlate them with operative or vaginal delivery. Some studies have been published regarding the diameters' variation with the shifting of the patient's posture. The positions used in the research for the analysis of changes in pelvis measurements are the same as those used for centuries to assist and promote childbirth.

This technical report is to define a method of measuring changes in classical pelvimetric external diameters in relation to the postural change of the subjects, taking into consideration the needs of the operators, the postural difficulties of pregnant women and the evidence acquired from instrumental research. It aims to propose a dynamic postural method suited to daily practice, according to the directives and principles of the classical external obstetric pelvimetry.